The present invention relates to insulating foam of the type used for constructing plaza decks or the like. Typically, plaza deck is comprised of a structural support deck, an overlying, waterproof membrane, an intervening foam insulation board, and a concrete wearing slab. Several problems with this plaza deck composite have been identified by and are well-known to the industry. First, moisture tends to accumulate between the concrete wearing slab and the waterproof membrane, compromising the insulating value of the foam insulation board and often causing the freeze/thaw spalling of the concrete wearing slab. In response to this problem, the common practice in the art has become the addition of a drainage layer between the foam insulation and the concrete wearing slab. In certain applications, an additional drainage layer between the foam insulation and the waterproof layer is also desirable. In either case, the drainage layer(s) mitigates the harmful affects of moisture accumulation in the foam insulation board.
Previously, the standard industry method called for the use of loose gravel or epoxy bound gravel as the drainage layer. However, U.S. Pat. Nos. 4,658,554 and 4,712,349 both disclose a foam insulation layer whose upper surface is sculpted to include a series of parallel drainage channels flanked by raised, rib-like walls. In both of these patents, it is further provided that the lower surface of the foam insulation board is laminated with a plastic film so as to prevent the migration of moisture vapor from the waterproof membrane through the interface between the insulation board and the concrete wearing slab. Both of these patents thus provide for the retardation of moisture accumulation as well as the drainage of accumulated moisture, without the use of loose or epoxy-bound gravel.
A second problem with the typical plaza deck composite, not addressed by either the '554 or '349 patents, is the addition of the concrete wearing slab. Since the concrete wearing slab must be laid directly on the/barn insulating layer, the standard practice was to form concrete wearing slabs at one location, ship them to the construction site, and place them upon the foam insulating board. One solution to this problem is offered by U.S. Pat. No. 5,067,298, which discloses a method whereby the concrete wearing slab can be formed directly at the construction site. A layer of fabric, interposed between the foam insulation layer and the wearing slab, permits wet concrete to be poured directly onto the insulation layer without clogging the drainage channels on the upper surface thereof.
U.S. Pat. No. 5,067,298 discloses providing parallel drainage channels on both the top and bottom surfaces of the loam. The '298 foam may also include perpendicular sets of parallel channels on one or both sides of the foam. However, top and bottom sets of channels are disclosed as being parallel (though claimed more broadly), creating a narrower loam board cross section between the bases of the parallel top and bottom channels, extending across the board width or length.